The present invention relates in general to integrated circuits, and in particular to an improved differential output driver circuit with monotonic output transitions.
A differential output driver typically includes a pair of separate output drivers respectively driving a complementary pair of output terminals in response to an input signal. Such differential output drivers can be found in a variety of circuit applications. Often, and in particular in telecommunication applications, the pair of output terminals are resistively coupled to each other. For example, an RS422 driver circuit is required to drive differential output terminals that are connected together by a termination resistor of about 100 Ohms. With the signals at the output terminals switching in opposite directions, this resistive coupling can give rise to glitches on the output signals during their transition from one binary state to another. That is, if the timing of the switching of the output transistors is not designed properly, the output of one driver that is active may cause the signal at the other output that may be tri-stated move in the same direction. This results in non-monotonic signal transitions at the outputs.
There are certain applications such as RS422 drivers that require monotonic output signal transitions. Therefore, there is a need for circuitry and methods that eliminate non-monotonic switching at the output of differential drivers.